fix: support compound file-types

[baod-rate]

Vim supports compound filetypes (see |'filetype'|):

When a dot appears in the value then this separates two filetype names.
This works both for filetype plugins and for syntax files. More than one dot may appear.

nvim-lspconfig currently always compares the full 'filetype' option against the configured filetypes. So buffers set to multiple filetypes will not match at all.

Fix utility functions to match against each individual filetype

[glepnir]

there has vim.fs module.

[baod-rate]

sorry, can you explain? I don't see anything in vim.fs that does this. vim.fs seems to deal mostly with filesystem operations. I'm not actually reading files here, I am only splitting and comparing filetype strings

[glepnir]

okay see vim.filetype moudle. vim.filetype.match will return the filetype if it already in default detect table or register by vim.filetype.add . we don't want add more utils function now

[baod-rate]

vim.filetype.match takes an existing buffer and returns the filetype (using the rules defined in filetype.lua). the result of that might be (for example) c.doxygen. see |'filetype'|:

						*'filetype'* *'ft'*
'filetype' 'ft'		string	(default "")
			local to buffer  |local-noglobal|
...
	Setting this option to a different value is most useful in a modeline,
	for a file for which the file type is not automatically recognized.
	Example, for in an IDL file: >c
		/* vim: set filetype=idl : */
<	|FileType| |filetypes|
	When a dot appears in the value then this separates two filetype
	names.  Example: >c
		/* vim: set filetype=c.doxygen : */
<	This will use the "c" filetype first, then the "doxygen" filetype.
	This works both for filetype plugins and for syntax files.  More than
	one dot may appear.
	This option is not copied to another buffer, independent of the 's' or
	'S' flag in 'cpoptions'.
	Only normal file name characters can be used, `/\*?[|<>` are illegal.

In other words:

local ft = vim.filetype.match({buf=0})
ft == "c.doxygen"
util.ft_matches(ft, 'idl') == false
util.ft_matches(ft, 'c') == true
util.ft_matches(ft, 'doxygen') == true

[glepnir]

you can also pass filename into match

        -- Using a filename without a buffer
        vim.filetype.match({ filename = 'main.lua' })

        -- Using file contents
        vim.filetype.match({ contents = {'#!/usr/bin/env bash'} })

[baod-rate]

yes, vim.filetype.match can take a filename and give us a filetype. but what we want is to take that filetype and check it against a list of filetypes (e.g. the ones supported by a particular lsp server).

i.e.

local ft = vim.filetype.match({ filename = 'main.lua' })
ft == "lua"
local filetypes_supported_by_current_client = { "lua", "sh", "c" }
util.ft_matches(ft, filetypes_supported_by_current_client) == true

Usually this would just be a == comparison but because a filetype can contain multiple filetypes (e.g. c.doxygen), we have to split it first.

local ft = vim.bo.filetype
ft == "yaml.ansible" -- this is not a filename! it is a _compound_ filetype
util.ft_matches(ft, "ansible") == true
util.ft_matches(ft, "yaml") == true

notice that vim.filetype.match doesn't help us do this comparison! it takes a buffer/file/filepath and gives us a filetype. but we don't need that. we have a filetype, it is provided by the caller. We are trying to match that against a list of acceptable filetypes, also provided by the caller.

[glepnir]

thanks for your kind reply . does register a filetype by using vim.filetype.add for a special file not make sense in user side ?

[baod-rate]

A completely unique type is not desirable because we want to use the existing behaviors defined for the primary filetype. see mfussenegger/nvim-ansible or pearofducks/ansible-vim. They both set ft=yaml.ansible.

You want ansible scripts to have the yaml filetype because that's what they are; we want (neo)vim to keep recognizing them as yaml files. if we set ft=ansible only, we lose the syntax highlighting/match_words/etc defined for yaml files.

But the plugin additionally sets various useful options like keywordprg/path/iskeyword/isfname for ansible file types. Hence the reason for multiple file types.

The problem is that right now, nvim-lspconfig diverges from standard vim behavior because filetype matching operates on the entire vim.bo.filetype as a whole, rather than splitting it into individual file types. And every server has to be configured for every possible combination of multiple filetypes. see:

nvim-lspconfig/lua/lspconfig/server_configurations/yamlls.lua

Lines 4 to 6 in a3d9395

	default_config = {
	cmd = { 'yaml-language-server', '--stdio' },
	filetypes = { 'yaml', 'yaml.docker-compose', 'yaml.gitlab' },

(notice that yaml.ansible is not included.

With this change, you can instead just specify yaml, and we'll match as long as one of your filetypes matches yaml

[justinmk]

this new function has no docstring explaining its purpose. and this PR has a wall of text discussing it.

how in the world is anyone supposed know when to use this

[baod-rate]

apologies, I didn't realize that it was unclear. I've added documentation. let me know if it's unclear